Micromechanical devices such as micromotors, microgears and deformable mirror devices often have moveable surfaces that contact one another, either constantly or intermittently. For example, a micromechanical deformable mirror device (DMD) typically contains an address electrode, a landing electrode, one or more support posts, and a deflectable beam. DMDs are primarily used in optical systems where the deflectable beam has a mirrored surface. DMDs, however, may be used in other applications such as accelerometers and the deflectable beam need not have a mirrored surface.
In the case of a DMD, a voltage is applied between the deflectable beam and the address electrode, causing an electrostatic attraction between the address electrode and the deflectable beam. This attraction causes the deflectable beam to deflect towards the address electrode until it contacts the landing electrode. When the charge is removed, the deflectable beam returns to its undeflected position.
Contact between elements in micromechanical devices may result in sticking. For example, in a DMD, the deflectable beam may stick in the deflected position after coming into contact with the landing electrode. Depending upon the duration of the sticking, this can cause a device malfunction. The frequent contacts between the deflectable beam and the landing electrode also tend to wear away the surface of the landing electrode thus decreasing the lifetime of the device.